I have a customer who is trying to LM5032 to produce a high powered converter. See his remarks:
We are in the process of developing a 2KW Standby Power Inverter for Emergency Lighting. The main Power Board is comprised of:
A PFC Boost Converter to charge up the +/- 190 Volt Bus while On Line.
A charger circuit to Charge the batteries while on Line (using one of the Boost Inductors)
An Inverter to Convert the +/- 190 Volt Bus to 120 VAC while On Line and On Battery.
An Interleaved Boost circuit to Convert the Battery Voltage to +/- 190 while On Battery.
The Attached Schematic shows the Interleaved Boost circuit components.
For Initial testing, only the components associated with L7 and L9 were loaded. (half the Power Devices). Also, Q3 was replaced with the same SIC diode as D12.
I have been testing for several weeks to obtain the best results with 3 circuit boards.
This has involved:
Different values for the current feedback resistors R60, R65 and capacitors C40,C44.
Different combinations of Snubbers for the Power Fets and Diodes.
Different filtering for the Power Supplies.
Different Gate resistors for the Fet Drivers.
Different values for the voltage feedback circuit of U10, C48,R51 and C47.
The attached picture #1, shows the current waveform at CS1, with the voltages across FETs. This is at 1800 watt load, and is interleaving properly with little current ripple measured at the Battery.
The attached picture #2 shows an identical loaded board, but not sharing properly.
I have tested different boards, under load conditions from 200 watt up to 3000 watts. Sometimes it works properly under light load but not heavy load, or vice versa. I had concluded that this is due to the high frequency (120 mhz) noise on the current feedback at CS1 and CS2. I attributed it to the switching Power Devices and Inductors.
I loaded a new board with only the LM5032 components and power supply. The current feedback resistors R60 and R65 tied to ground with 12 resistor.
The attached picture #3 and 4 shows waveforms at CS1 and Out1. The high frequency ringing is present at rising falling edges of each output and at CS1. I have tried different power supply filtering and even substituted the power supply DC-DC converter with a Battery and no change.
Any ideas on how to suppress the ringing at the CS pins?
Is this normally what is seen?
I feel if this ringing wasn’t so large the circuit would work well.
I did not want to post the schematic, but I can send it to you along with the scope shots that are referenced below. Please let me know if you can look at this and try to find the issue.
Thanks for your help with this!
Richard Elmquist
